This invention relates to the processing of animal and vegetable waste by composting, on farms, and in particular to the automation and improvement of agricultural composting.
The traditional systems for the disposal of waste agricultural materials such as pig manure are being increasingly criticised on environmental grounds. An aim of the invention is to make it possible to dispose of animal manure, especially pig manure, by adding the manure into a composting system. The systems as described herein are aimed at converting pig manure and other organic waste materials into useful material such as fertiliser, in a manner that achieves the conversion more economically and efficiently (and therefore more cost-effectively) than has been the case hitherto.
The mechanically-sophisticated composting systems as described herein, though developed mainly for disposing of pig manure, also dispose of the solid waste material, i.e the material other than the pig manure, in the compost. The systems can be utilised for disposing of vegetable and animal waste generally, as compost.
The scope of the invention is defined by the accompanying claims.
Composting systems of the type with which the invention is concerned include bays or troughs, in which the solid material to be composted is heaped. It is an aim of the present invention to add mechanical sophistication to the processing apparatus, which makes it possible to control the composting system parameters. It is an aim of the invention to control and manipulate the process so closely that differences in conditions between different areas of the batch of material can be evened out, thereby rendering the batch more homogeneous. Concentration can be brought to bear on those areas of the batch where composting is proceeding only slowly, whereby all the portions of the batch can gradually be brought to maximum efficiency. In a conventional composting system, it is the presence of slow-to-react regions that delay the completion of the batch. An aim of the invention is to eliminate the slow-to-react regions. That being done, the effect is to reduce the overall time of an aerobic composting session from the usual minimum thirty days to, often, as little as twenty days. With conventional systems, only some regions of a batch were composted at twenty days; with the invention, the aim is to have the whole batch composted in that time.
The invention is mainly intended for use with batch-processing of compost, as distinct from continuous processing. In continuous processing, typically, fresh material to be composted is added at one end to the trough every day, and the material gradually works its way along the trough (by mechanical manipulation) to the other end of the trough, in a sufficient number of days that composting is completed. However, it is difficult to achieve a consistent output with a continuous process, in that, since Tuesday""s material remains separated from Monday""s material throughout the process, it is difficult to even out variations in the material. With batch processing, the material can be mixed together, which evens out the day-to-day variations. An aim of the invention is to enable the mechanical manipulation needed for mixing the material (which thereby evens out variations in the material), to be combined with the mechanical manipulation needed for turning, lifting, and aerating the material (which thereby promotes the bio-chemical composting reactions).
The apparatus as described herein may be used predominantly as a means for disposing of the pig manure. Pig manure being mainly liquid, it is difficult and expensive to turn pig manure into useful fertiliser. Pig manure generally will not compost itself of its own accord, but rather it has to be mixed with some solid carbonaceous vegetable matter in order to create the conditions in which the (aerobic) micro-biological composting reactions can commence.
In treating the pig manure, if the required carbonaceous vegetable matter is available on the farm (corn cobs, straw, etc), that can be used. If not, solid carbonaceous material should be brought in. Brought-in material can be e.g sawdust from a sawmill; carbonaceous material diverted from a landfill, e.g leaves, paper, etc; or such other carbonaceous degradable material as can be obtained cheaply.
The mechanical sophistication needed for the tight control of the process is achieved by arranging for an apron to traverse back and forth through the composting material. The apron carries moving blades for lifting and turning and aerating the composting material. As described, the apron is two-sided; that is to say, the apron can be set to operate in either direction along the trough, and the blades are arranged for direct contact with the material in both directions of traverse.
With the use of the apparatus as described herein, because of the ability for close control of the composting processes, it becomes worthwhile to monitor the parameters of the composting reactions closely, and to make changes accordingly. Treatment materials can be added, aeration can be applied, traverse speeds and traverse frequency can be changed, and so forth. The apparatus can be adapted for slowing down the traverse speed of the apron in areas where aeration is not so advanced, enabling an increased manipulation of the material, to break the material up and expose it to the air to a greater extent in those areas.
The apparatus can be set for traversing the apron back and forth. That is to say, the apparatus is such that the apron can be reversed. Now, in this kind of processing, the apron lies at a substantial angle to the vertical, typically thirty degrees; so, in order to reverse the apron, the apron has to go through a position where the apron is upright. As such, the apron has to be lifted (i.e raised up off the floor of the trough) to enable the apron to pass through the upright position. Means for raising the apron, for reversing the apron, are provided in the apparatus as described herein.
The ability to raise the apron means the apron can be traversed back and forth over and through the composting material. The system can be made very sophisticated, with instrumentation, fine tuning of liquid spray to achieve moisture content, air blasting to give the right oxygen content, and, as mentioned, the means to render the batch as homogenous as possible. With conventional systems, it was not possible to refine the composting process, because close control of the process was not available. It is an aim of the invention that the system now can be refined to the extent as to make it worthwhile to automate the control of the composting process.
Preferably, in the case where the composting process is being carried out primarily as a way of disposing of liquid manure, the spreading of the liquid manure onto the solid carbonaceous material can be automated and controlled. The material can be monitored for moisture content, and the liquid sprayed accordingly.
Patent publications U.S. Pat. No. 5,459,071 (Finn, October 1995); U.S. Pat. No. 5,405,780 (Hamilton, April 1995); and U.S. Pat. No. 5,149,196 (Piacentino, September 1992) might be considered relevant to the present invention. However, the apparatus illustrated in these publications have not had the ability for the close control of the parameters that comes from back and forth movement of the apron, as described herein.